This invention relates to ionic conjugates including inorganic particles and macromolecules, and more particularly to an electrostatic conjugate useful in detecting the presence or absence of specific species, such as for detecting a biological target.
Labeling of biological molecules using fluorescent tags is a common and useful practice in biological science. Fluorescent small molecules (conventional organic dyes) are used in both single and simultaneous multiple detection approaches. However, biological tagging using organic fluorophores has significant limitations. Fluorescent molecules tend to have narrow absorption spectra and their emission spectra are usually broad and exhibit red tailing, making simultaneous quantitative evaluation of relative amounts of different probes present in the same sample difficult due to spectral cross talk between various detection channels. Furthermore, any desired variations of the absorption and/or emission spectra of tagged bioconjugates require the use of distinct molecular labels with attendant synthesis and bioconjugation challenges. Nonetheless, the use of multiple labels has achieved a considerable level of sophistication, as demonstrated by recent flow cytometry work involving a three-laser system and eight-color marking scheme to simultaneously measure a total of 10 parameters on cellular antigens.